Home › Guides › API number lookup
Look up an oil or gas well by API number
Type the number, with or without dashes, into the search box at the top of any page. If one well matches you go straight to its page; if several match (a well and its sidetracks), you get the list.
How to read an API number
| Digits | Means | Example: 42-329-48625 |
|---|---|---|
| 1–2 | State | 42 = Texas |
| 3–5 | County (odd numbers, in alphabetical order) | 329 = Midland County |
| 6–10 | The well, unique within the county | 48625 |
| 11–12 | Sidetrack (00 = original hole), where used | — |
| 13–14 | Event, such as a recompletion, where used | — |
API state codes for the states we cover
| State | Code | Wells on WellheadMap |
|---|---|---|
| Alaska | 50 | 12,059 |
| Arizona | 02 | 1,115 |
| California | 04 | 242,559 |
| Colorado | 05 | 124,446 |
| Florida | 09 | 1,466 |
| Illinois | 12 | 207,298 |
| Kansas | 15 | 519,691 |
| Louisiana | 17 | 247,329 |
| Michigan | 21 | 58,957 |
| Mississippi | 23 | 34,932 |
| Missouri | 24 | 10,368 |
| Montana | 25 | 42,049 |
| Nevada | 27 | 1,070 |
| New Mexico | 30 | 136,399 |
| New York | 31 | 46,525 |
| North Dakota | 33 | 44,005 |
| Ohio | 34 | 238,601 |
| Oklahoma | 35 | 457,181 |
| Pennsylvania | 37 | 224,491 |
| South Dakota | 40 | 2,137 |
| Texas | 42 | 1,397,551 |
| Utah | 43 | 38,936 |
| West Virginia | 47 | 146,297 |
| Wyoming | 49 | 207,791 |
Federal offshore wells use their own area codes. Indiana, Arkansas and Virginia list most wells by a state permit number instead, so search those states by permit number.
Questions
What is an API well number?
A unique number given to each oil or gas well in the United States, following a standard first set by the American Petroleum Institute. It stays with the well for life, even when the operator changes.
How many digits is an API number?
10 digits for the well itself (2 for the state, 3 for the county, 5 for the well). Some states add 2 digits for a sidetrack and 2 for an event such as a recompletion, making 14.
Can I search with only part of an API number?
Yes. Type at least the first 8 digits and WellheadMap lists every well that starts with them. In Texas you can also type the 8 digits without the leading 42.
Where does the API number come from?
The state oil and gas regulator assigns it when the well is permitted. Each well page on WellheadMap names that agency and links to its record where the state offers one.
What if a well has no API number?
Some states, and many older wells, use only a state permit or serial number. Type that number in the search box instead.